Nitrosamines, hydrazines, nitramines, azo- and azoxy-compounds are widely used in biological and chemical research. Many of these compounds are potential carcinogens. In particular, N-nitrosodimethylamine (NDMA) is a known carcinogen. A laboratory in which these compounds are being manipulated typically generates potentially carcinogenic refuse in a wide variety of forms, including unused drinking water solutions from animal bioassay experiments, rinsings from distillation apparatus, and aged analytical standards. Because these compounds are known or suspected carcinogens and are found to be generally more toxic than their parent amines, a reliable means for destroying them should be available, including a means to render them innocuous in waste materials prior to disposal. Complete oxidative degradation in an efficient incinerator would seem to be the general approach to destruction of organic carcinogens, but this method can be impractical, especially for large volumes of non-combustible (e.g., aqueous) materials.
Methods for disposing of nitrosamines have been the subject of a substantial amount of experimental inquiry. It has been recommended (Gangolli, Shilling and Lloyd, 1974) that basified aqueous solutions of nitrosamines be degraded by exposing them to aluminum foil; however, we have found (Emmett, Michejda, Sansone and Keefer, 1980) that, while the NDMA is quantitatively consumed by this method, the primary reaction product is N,N-dimethylhydrazine, which is itself a carcinogen in mice.
Photodegradation using ultra violet light has been suggested (Emmett et al, supra) as a method for disposing of NDMA. Experimental results, however, have shown the degradation to be incomplete. In addition, after the removal of the light source, resynthesis reactions are known to take place. Furthermore, the products of photodegradation are also potential carcinogens.
A method which has been recommended (Seebach and Wykypiel, 1979) for the complete reduction of nitrosamines to the less toxic amines is a two-step procedure by which the nitrosamine is first converted to the hydrazine using lithium aluminum hydride in an anhydrous ethereal solvent. The hydrazine is then hydrogenolyzed to the amine in the presence of Raney-nickel under a hydrogen atmosphere. The nitrosamine is first reduced using lithium aluminum hydride, under an inert atmosphere of argon or nitrogen, by refluxing for 3 to 4 hours while heating. The vessel is then placed in an ice bath and an aqueous ammonium solution is added until gas evolution ceases. Thereafter, in a second step, after filtering and washing with hot tetrahydrofuran, the Raney-nickel is added to the solution thus obtained and a hydrogen atmosphere maintained. These reactants are stirred for 10 to 14 hours to effect the conversion to the amine. The conversion is not always quantitative.
We have found a one-step method for the successful quantitative conversion of NDMA to the relatively nontoxic dimethylamine in a variety of solvents commonly used with nitrosamines, including water, mineral oil and dichloromethane, without the hydrogen atmosphere previously used for these and similar reduction processes. This nickel-aluminum-alkali system is a broadly applicable approach to hazard control for work with nitrosamines, hydrazines, nitramines azo- and azoxy-compounds. Although we have found the reduction reaction to progress rapidly, as quantified in the examples below, when treating these materials for disposal we recommend using a reaction time of 24 hours to assure complete conversion to the amine.
This reaction can also be used for the synthesis of amines by the hydrogenation and breaking of N--N or N.dbd.N bonds.